A multimode dual-standby dual-active terminal of Long Term Evolution (LTE) and Global System for Mobile communication (GSM) can provide users with a mobile voice call service and a high-speed data service. The voice is transmitted by means of a GSM network, and the data is transmitted by means of an LTE network.
In the related art, a dual-radio-frequency solution can solve data service interruption, switching or suspending caused by the Circuit Switched Fallback (CSFB) technology. Furthermore, the technical complexity of the dual-radio-frequency solution is relatively low, so the dual-radio-frequency solution is a selectable solution for the early development of voice service of the LTE.
FIG. 1 is a traditional architecture diagram of using a radio-frequency dual-chip to implement an LTE/UMTS/GSM multimode dual-active terminal. As shown in FIG. 1, the LTE/GSM multimode dual-active terminal is mainly composed of a digital baseband chip, an LTE radio-frequency module, a GSM radio-frequency module, and a power management chip. The LTE radio-frequency module uses two antennae, one of which is used as a primary channel for reception and transmission, and the other is used as a secondary channel for reception. The GSM radio-frequency module is composed of an antenna; the GSM900 and the DCS1800 share an antenna.
In the multimode terminal shown in FIG. 1, the interference between transmission at GSM900 band and reception at Band 41 band is shown in FIG. 2. A GSM900 transmission signal is mainly composed of a GSM900 useful signal, each harmonic signal of a transmission signal, and a broadband white noise of the transmission signal. The GSM900 third harmonic (2640 MHz-2745 MHz) is partly in the Band 7/41 reception band.
In the multimode terminal shown in FIG. 1, the traditional interference between transmission at GSM900 band and reception at Band 41 band is shown in FIG. 3. There is a GSM900 useful signal, the second harmonic, and the third harmonic (2640 MHz-2745 MHz) at a GSM transmission port A. At the point A, the power of the useful signal is 33 dBm, and the third-harmonic intensity is about −50 dBm. If the isolation between a GSM antenna and an LTE antenna is about −15 dB, the power of the GSM useful signal received at an LTE reception port B is about 18 dBm, and the GSM third-harmonic intensity is about −65 dBm. The third harmonic of an LTE antenna switch is about 85 dBc, and an in-band insertion loss is about 1 dB; after the GSM useful signal passes the switch, the third harmonic generated at the point C is about −67 dBm, the total third harmonic of the GSM useful signal at the point C is about −63.5 dBm, and the power of the GSM useful signal is about 17 dBm. The insertion loss of a Band 41 filter is about 3 dB, the insertion loss near 900 MHz is about 45 dB, the power of the useful signal of the GSM band which is received at the Band 41 reception port D of the LTE chip is about −28 dBm, and the third harmonic of the GSM band is about −70 dBm. The Band 41 reception port will be interfered by the signal in the GSM band and its third harmonic.
To sum up, in the existing dual-radio-frequency solution, a signal transmitted by a module will interfere reception of signals by another module.
There is yet no effective solution for addressing the problem in the related art that two communication modules in a multimode dual-standby dual-active terminal will interfere with each other.